| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | dilaz03(at)gmail(dot)com |
| Cc: | pgsql-bugs(at)postgresql(dot)org |
| Subject: | Re: BUG #14753: Bad selectivity estimation with functional partial index |
| Date: | 2017-07-19 15:45:23 |
| Message-ID: | 27613.1500479123@sss.pgh.pa.us |
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| Lists: | pgsql-bugs |
dilaz03(at)gmail(dot)com writes:
> Postgres doesn't see corresponding stats tuple for functional partial
> index.
That's not a bug, it's intentional, per the comment in examine_variable():
* Has it got stats? We only consider stats for
* non-partial indexes, since partial indexes probably
* don't reflect whole-relation statistics; the above
* check for uniqueness is the only info we take from
* a partial index.
It's theoretically possible that we could do something useful with stats
from a partial index, but it would require a lot of shaky assumptions
I'm afraid.
regards, tom lane
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